SUBELEMENT T5 Electrical principles: math for electronics; electronic principles; Ohm s Law 4 Exam Questions - 4 Groups

Transcription

1 SUBELEMENT T5 Electrical principles: math for electronics; electronic principles; Ohm s Law 4 Exam Questions - 4 Groups 1

2 T5A Electrical principles, units, and terms: current and voltage; conductors and insulators; alternating and direct current 2

3 While one does not have to be an Electronic Engineer to pass the Technician Class ham license (That comes later with the General and Extra Class ham licenses 3

4 (Just kidding!), you do have to know a few of the basics. That is what this course will cover. Just the basics. 4

5 Voltage is the force that causes electrons to flow in an electrical circuit. The Volt is also called EMF for Electro Motive Force and is measured with a volt meter. The volt is the basic unit of EMF. In a schematic or block drawing, the letter V is used to indicate volts. In an electronic formula, the letter E is used to indicate voltage. 5

6 Electrical current is measured in amperes. Current is the name for the flow of electrons through an electrical circuit in which voltage causes to flow. An ammeter is used to measure current. The letter I is used in electrical formulas to indicate the amount of current being used. 6

7 Electrical power is measured in watts. Power is the rate at which electrical energy is consumed. Example: A 100 watt light bulb consumes 100 watts of power to generate light. 7

8 T5A01 Electrical current is measured in which of the following units? A. Volts B. Watts C. Ohms D. Amperes 8

9 T5A01 Electrical current is measured in which of the following units? D. Amperes 9

10 T5A02 Electrical power is measured in which of the following units? A. Volts B. Watts C. Ohms D. Amperes 10

11 T5A02 Electrical power is measured in which of the following units? B. Watts 11

12 T5A03 What is the name for the flow of electrons in an electric circuit? A. Voltage B. Resistance C. Capacitance D. Current 12

13 T5A03 What is the name for the flow of electrons in an electric circuit? D. Current 13

14 T5A10 Which term describes the rate at which electrical energy is used? A. Resistance B. Current C. Power D. Voltage 14

15 T5A10 Which term describes the rate at which electrical energy is used? C. Power 15

16 T5A05 What is the electrical term for the electromotive force (EMF) that causes electron flow? A. Voltage B. Ampere-hours C. Capacitance D. Inductance 16

17 T5A05 What is the electrical term for the electromotive force (EMF) that causes electron flow? A. Voltage 17

18 T5A11 What is the basic unit of electromotive force? A. The volt B. The watt C. The ampere D. The ohm 18

19 T5A11 What is the basic unit of electromotive force? A. The volt 19

20 Direct current is the name for a current that flows only in one direction. Examples of Direct Current or DC is a 12 volt car battery, Flashlight batteries, and etc. 20

21 Alternating current is the name for a current that reverses direction on a regular basis. An example of Alternating Current, or AC is the typical house electrical outlet. 21

22 Frequency is the term that describes the number of times per second that an alternating current reverses direction. 22

23 A mobile transceiver usually requires about 12 volts. This is true for most modern day ham equipment. 23

24 To use a mobile transceiver, or other 12 volt radio in the house, one would usually use a Power Supply. 24

25 A power supply simply converts the 117 Volts AC house outlet to 12 Volts DC that the radio needs to operate properly. 25

26 T5A04 What is the name for a current that flows only in one direction? A. Alternating current B. Direct current C. Normal current D. Smooth current 26

27 T5A04 What is the name for a current that flows only in one direction? B. Direct current 27

28 T5A06 How much voltage does a mobile transceiver usually require? A. About 12 volts B. About 30 volts C. About 120 volts D. About 240 volts 28

29 T5A06 How much voltage does a mobile transceiver usually require? A. About 12 volts 29

30 T5A09 What is the name for a current that reverses direction on a regular basis? A. Alternating current B. Direct current C. Circular current D. Vertical current 30

31 T5A09 What is the name for a current that reverses direction on a regular basis? A. Alternating current 31

32 T5A12 What term describes the number of times per second that an alternating current reverses direction? A. Pulse rate B. Speed C. Wavelength D. Frequency 32

33 T5A12 What term describes the number of times per second that an alternating current reverses direction? D. Frequency 33

34 There are many metals that make good conductors: silver, gold, copper, aluminum, etc. 34

35 You will only need to remember one though. Copper is a good electrical conductor. 35

36 There are many good insulators as well: Glass, plastic, even air. Again, you will only need to remember one for the exam. 36

37 Glass is a good electrical insulator 37

38 T5A07 Which of the following is a good electrical conductor? A. Glass B. Wood C. Copper D. Rubber 38

39 T5A07 Which of the following is a good electrical conductor? C. Copper 39

40 T5A08 Which of the following is a good electrical insulator? A. Copper B. Glass C. Aluminum D. Mercury 40

41 T5A08 Which of the following is a good electrical insulator? B. Glass 41

42 T5B Math for electronics: conversion of electrical units; decibels; the metric system 42

43 An ampere is a very large unit for most of our electrical work. Hams usually measure currents using the smaller scale of milliamperes. 43

44 Milliamperes is simply 1 onethousandth of an ampere. 1 ampere is 1000 milliamperes. 44

45 The easiest way to convert an ampere is to simply move the decimal place to the right by three spaces. 45

46 1 ampere equals 1000 milliamperes. 1.5 ampere equals 1,500 milliamperes. 46

47 Or you can do it the hard way and multiply amperes by 1,000: 1 X 1,000 = 1,000 milliamperes. 1.5 X 1,000 = 1,500 milliamperes. 47

48 If an ammeter calibrated in amperes is used to measure a 3000-milliampere of current, the reading would be 3 amperes. 48

49 To convert milliamperes to amperes, simply move the decimal place to the left by three. Or do the math: 3,000 / 1,000 equals 3 ampere. 49

50 Here are some other need to know conversions: 50

51 Milli (as in above): 1 onethousandth of a quantity. Divide or multiply by 1,000 or simply move the decimal place to the right or left by 3 places. Micro: is 1 millionth of a quantity. Divide by or multiply by 1,000,000 or simply move the decimal place to the right or left by 6 places. 51

52 Pico: 1 trillionth of a quantity. Kilo: 1 thousand of a quantity. 1,000 volts is 1 KV (Kilovolt) 1,000 hertz is 1 Khz. (Kilohertz) To convert 1 Kilovolt to volts, simply move the decimal place to the right by 3. To convert Volts to Kilovolts, simply move the decimal place to the left by three. 52

53 Mega: 1 million of a quantity. 1 MHz is 1,000,000 Hertz. To convert from Hertz to Mega Hertz (Mhz) simply move the 6 spaces to the left. To convert from Mega Hertz to Hertz, simply move the decimal place to the right 6 spaces. 53

54 1500 khz is another way to specify a radio signal frequency of 1,500,000 hertz. One thousand volts are equal to one kilovolt. One one-millionth of a volts is equal to one microvolt. 54

55 0.5 watts is equivalent to 500 milliwatts. One microfarads is equal to 1,000,000 picofarads. 55

56 T5B01 How many milliamperes is 1.5 amperes? A. 15 milliamperes B. 150 milliamperes C. 1,500 milliamperes D. 15,000 milliamperes 56

57 T5B01 How many milliamperes is 1.5 amperes? C. 1,500 milliamperes (move the decimal place to the right by 3 spaces.) or (1.5 x 1000 = 1500) 57

58 T5B02 What is another way to specify a radio signal frequency of 1,500,000 hertz? A khz B MHz C. 15 GHz D. 150 khz 58

59 T5B02 What is another way to specify a radio signal frequency of 1,500,000 hertz? A khz (move the decimal place to left 3 spaces) or ( 1,500,00 / 1000 = 1500) 59

60 T5B03 How many volts are equal to one kilovolt? A. One one-thousandth of a volt B. One hundred volts C. One thousand volts D. One million volts 60

61 T5B03 How many volts are equal to one kilovolt? C. One thousand volts 61

62 T5B04 How many volts are equal to one microvolt? A. One one-millionth of a volt B. One million volts C. One thousand kilovolts D. One one-thousandth of a volt 62

63 T5B04 How many volts are equal to one microvolt? A. One one-millionth of a volt 63

64 T5B05 Which of the following is equivalent to 500 milliwatts? A watts B. 0.5 watts C. 5 watts D. 50 watts 64

65 T5B05 Which of the following is equivalent to 500 milliwatts? B. 0.5 watts (move the decimal place to the left 3 places) or (500/1,000 =.5) 65

66 T5B06 If an ammeter calibrated in amperes is used to measure a 3000-milliampere current, what reading would it show? A amperes B. 0.3 amperes C. 3 amperes D. 3,000,000 amperes 66

67 T5B06 If an ammeter calibrated in amperes is used to measure a 3000-milliampere current, what reading would it show? C. 3 amperes (move the decimal place to the left 3 places) or (3,000 / 1,000 = 3) 67

68 T5B08 How many microfarads are 1,000,000 picofarads? A microfarads B. 1 microfarad C microfarads D. 1,000,000,000 microfarads 68

69 T5B08 How many microfarads are 1,000,000 picofarads? B. 1 microfarad (1 million = 1 micro) 69

70 If a frequency readout calibrated in megahertz shows a reading of MHz, it would show 3525 khz if it were calibrated in kilohertz. 70

71 The following frequency is equal to 28,400 khz: MHz 71

72 A frequency readout showing a reading of 2425 MHz is GHz 72

73 T5B07 If a frequency readout calibrated in megahertz shows a reading of MHz, what would it show if it were calibrated in kilohertz? A khz B khz C khz D. 3,525,000 khz 73

74 T5B07 If a frequency readout calibrated in megahertz shows a reading of MHz, what would it show if it were calibrated in kilohertz? C khz (move the decimal place to the right 3 places) or (3.525 x 1,000 = 3525) 74

75 T5B12 Which of the following frequencies is equal to 28,400 khz? A MHz B MHz C MHz D khz 75

76 T5B12 Which of the following frequencies is equal to 28,400 khz? A MHz 76

77 T5B13 If a frequency readout shows a reading of 2425 MHz, what frequency is that in GHz? A GHZ B GHz C GHz D GHz 77

78 T5B13 If a frequency readout shows a reading of 2425 MHz, what frequency is that in GHz? C GHz 78

79 We use decibels when we are describing power ratios. A good example in ordinary life would be a rock band at the local high school. It is really loud! What high school rock band wouldn t be! 79

80 If you lower the loudness by half, you would be lowering the loudness by 3 decibels, or db for short. 80

81 If, heaven forbid, you wanted to make the band twice as loud, you would need to up the volume by 3 db! 81

82 The approximate amount of change, measured in decibels (db), of a power increase from 5 watts to 10 watts is 3dB. The approximate amount of change, measured in decibels (db), of a power decrease from 12 watts to 3 watts is -6dB. ( take it in steps: 3db would be 6 watts, then another 3db would be 3 watts.) The approximate amount of change, measured in decibels (db), of a power increase from 20 watts to 200 watts is 10dB. 82

83 T5B09 What is the approximate amount of change, measured in decibels (db), of a power increase from 5 watts to 10 watts? A. 2 db B. 3 db C. 5 db D. 10 db 83

84 T5B09 What is the approximate amount of change, measured in decibels (db), of a power increase from 5 watts to 10 watts? B. 3 db 84

85 T5B10 What is the approximate amount of change, measured in decibels (db), of a power decrease from 12 watts to 3 watts? A. -1 db B. -3 db C. -6 db D. -9 db 85

86 T5B10 What is the approximate amount of change, measured in decibels (db), of a power decrease from 12 watts to 3 watts? C. -6 db 86

87 T5B11 What is the approximate amount of change, measured in decibels (db), of a power increase from 20 watts to 200 watts? A. 10 db B. 12 db C. 18 db D. 28 db 87

88 T5B11 What is the approximate amount of change, measured in decibels (db), of a power increase from 20 watts to 200 watts? A. 10 db 88

89 T5C - Electronic principles: capacitance; inductance; current flow in circuits; alternating current; definition of RF; DC power calculations; impedance 89

90 The ability to store energy in an electric field is called capacitance. 90

91 A capacitor consists of two or more conductors separated by some sort of insulator. 91

92 The basic unit of capacitance is the farad. 92

93 The ability to store energy in a magnetic field is called inductance. 93

94 The basic unit of inductance is the Henry. 94

95 An inductor is often made by wrapping wire around a coil form. Sometimes however, self- supporting wire can simply be formed into a coil of 1 or more turns. 95

96 The greater the number of turns, the greater the inductance. 96

97 A resistor is used to oppose the flow of current in a DC circuit and is measured in ohms. 97

98 Resistors can be of fixed value or variable. An example of a variable resistor would be the volume control on a radio. 98

99 A variable resistor is also called a potentiometer. 99

100 T5C01 What is the ability to store energy in an electric field called? A. Inductance B. Resistance C. Tolerance D. Capacitance 100

101 T5C01 What is the ability to store energy in an electric field called? D. Capacitance 101

102 T5C02 What is the basic unit of capacitance? A. The farad B. The ohm C. The volt D. The henry 102

103 T5C02 What is the basic unit of capacitance? A. The farad 103

104 T5C03 What is the ability to store energy in a magnetic field called? A. Admittance B. Capacitance C. Resistance D. Inductance 104

105 T5C03 What is the ability to store energy in a magnetic field called? D. Inductance 105

106 T5C04 What is the basic unit of inductance? A. The coulomb B. The farad C. The henry D. The ohm 106

107 T5C04 What is the basic unit of inductance? C. The henry 107

108 Hertz is the unit of frequency. The hertz is one cycle of Alternating Current. The voltage outlet of your house is 117 Volts AC. 108

109 The frequency of the AC is 60 Hertz, meaning the current alternates at a rate of 60 times per second. 109

110 RF is the abbreviation that refers to radio frequency signals of all types. Radio waves is the usual name for electromagnetic waves that travel through space. 110

111 T5C05 What is the unit of frequency? A. Hertz B. Henry C. Farad D. Tesla 111

112 T5C05 What is the unit of frequency? A. Hertz 112

113 T5C06 What does the abbreviation RF refer to? A. Radio frequency signals of all types B. The resonant frequency of a tuned circuit C. The real frequency transmitted as opposed to the apparent frequency D. Reflective force in antenna transmission lines 113

114 T5C06 What does the abbreviation RF refer to? A. Radio frequency signals of all types 114

115 T5C07 What is a usual name for electromagnetic waves that travel through space? A. Gravity waves B. Sound waves C. Radio waves D. Pressure waves 115

116 T5C07 What is a usual name for electromagnetic waves that travel through space? C. Radio waves 116

117 You will need to know the power formulas for the test. Using the pie chart is one of the easiest ways to remember these three formulas. 117

118 During the exam will be given a blank page of paper in which you may do your calculations on. When the exam begins, you may draw this pie chart. 118

119 The pie chart itself is easy to remember because it actually spells PIE. All you need to remember is that the P goes on top and the I and E goes on the bottom. 119

120 120

121 Power (P) equals voltage (E) multiplied by current (I) is the formula used to calculate electrical power in a DC circuit. (Here are the power formulas:: P = E X I E = P / I I = P / E) 121

122 If one needs to know the power, just cover up P and you will see: I X E. 122

123 Looking for the Current? Cover up I and you will see: P / E. 123

124 For Volts, cover up E and you will see: P / I. 124

125 138 watts of power is being used in a circuit when the applied voltage is 13.8 volts DC and the current is 10 amperes (13.8 x 10 = 138) 125

126 30 watts of power is being used in a circuit when the applied voltage is 12 volts D and the current is 2.5 amperes. (12 x 2.5 = 30) 126

127 10 amperes are flowing in a circuit when the applied voltage is 12 volts and the load is 120 watts. (120 / 12 = 10) 127

128 T5C08 What is the formula used to calculate electrical power in a DC circuit? A. Power (P) equals voltage (E) multiplied by current (I) B. Power (P) equals voltage (E) divided by current (I) C. Power (P) equals voltage (E) minus current (I) D. Power (P) equals voltage (E) plus current (I) 128

129 T5C08 What is the formula used to calculate electrical power in a DC circuit? A. Power (P) equals voltage (E) multiplied by current (I) 129

130 T5C09 How much power is being used in a circuit when the applied voltage is 13.8 volts DC and the current is 10 amperes? A. 138 watts B. 0.7 watts C watts D. 3.8 watts 130

131 T5C09 How much power is being used in a circuit when the applied voltage is 13.8 volts DC and the current is 10 amperes? A. 138 watts 131

132 T5C10 How much power is being used in a circuit when the applied voltage is 12 volts DC and the current is 2.5 amperes? A. 4.8 watts B. 30 watts C watts D watts 132

133 T5C10 How much power is being used in a circuit when the applied voltage is 12 volts DC and the current is 2.5 amperes? B. 30 watts 133

134 T5C11 How many amperes are flowing in a circuit when the applied voltage is 12 volts DC and the load is 120 watts? A. 0.1 amperes B. 10 amperes C. 12 amperes D. 132 amperes 134

135 T5C11 How many amperes are flowing in a circuit when the applied voltage is 12 volts DC and the load is 120 watts? B. 10 amperes 135

136 Impedance is a measure of the opposition to AC current flow in a circuit and is measured in Ohms. 136

137 T5C12 What is meant by the term impedance? A. It is a measure of the opposition to AC current flow in a circuit B. It is the inverse of resistance C. It is a measure of the Q or Quality Factor of a component D. It is a measure of the power handling capability of a component 137

138 T5C12 What is meant by the term impedance? A. It is a measure of the opposition to AC current flow in a circuit 138

139 T5C13 What are the units of impedance? A. Volts B. Amperes C. Coulombs D. Ohms 139

140 T5C13 What are the units of impedance? D. Ohms 140

141 T5D Ohm s Law: formulas and usage 141

142 Using Ohm s law, one can calculate the value of Resistance, Current, or Voltage as long as two of the values are known. 142

143 The formula Current (I) equals voltage (E) divided by resistance (R).is used to calculate current in a circuit. 143

144 The formula Voltage (E) equals current (I) multiplied by resistance (R) is used to calculate voltage in a circuit. 144

145 The formula Resistance (R) equals voltage (E) divided by current (I) is used to calculate resistance in a circuit. 145

146 Just as in the Power calculations, Ohm s law is easy to remember by using a pie chart: 146

147 147

148 An easy trick to remember this chart is to realize that the letters E, I, and R are in a alphabetical order and the first Letter E is on top. 148

149 As with the power chart, one may draw this chart on your scratch paper once the test begins. 149

150 Similar to the Power chart, just cover up the missing item to see how to solve the problem. 150

151 The resistance of a circuit in which a current of 3 amperes flows through a resistor connected to 90 volts is 30 ohms. (R = E / I: 90 / 3 = 30 Ohms) 151

152 The resistance in a circuit for which the applied voltage is 12 volts and the current flow is 1.5 amperes is 8 ohms. (R = E / I: 12 / 1.5 = 8 Ohms) 152

153 The resistance of a circuit that draws 4 amperes from a 12-volt source is 3 ohms. (R = E/I: 12 / 4 = 3 Ohms) 153

154 The current flow in a circuit with an applied voltage of 120 volts and a resistance of 80 ohms is 1.5 amperes. (I = E / R: 120 / 80 = 1.5 Amps) 154

155 The current flowing through a 100-ohm resistor connected across 200 volts is 2 amperes. (I = E / R: 200 / 100 = 2 Amps) 155

156 The current flowing through a 24-ohm resistor connected across 240 volts 10 amperes. (I = E / R: 240 / 24 = 10 Amps) 156

157 The voltage across a 2-ohm resistor if a current of 0.5 amperes flows through it is 1 volt. (E = I X R: 0.5 X 2 = 1 Volt) 157

158 The voltage across a 10-ohm resistor if a current of 1 ampere flows through it is 10 volts. (E = I X R: 1 X 10 = 10 Volts) 158

159 The voltage across a 10-ohm resistor if a current of 2 amperes flows through it 20 volts. (E = I / R: 2 X 10 = 20 Volts) 159

160 T5D01 What formula is used to calculate current in a circuit? A. Current (I) equals voltage (E) multiplied by resistance (R) B. Current (I) equals voltage (E) divided by resistance (R) C. Current (I) equals voltage (E) added to resistance (R) D. Current (I) equals voltage (E) minus resistance (R) 160

161 T5D01 What formula is used to calculate current in a circuit? B. Current (I) equals voltage (E) divided by resistance (R) 161

162 T5D02 What formula is used to calculate voltage in a circuit? A. Voltage (E) equals current (I) multiplied by resistance (R) B. Voltage (E) equals current (I) divided by resistance (R) C. Voltage (E) equals current (I) added to resistance (R) D. Voltage (E) equals current (I) minus resistance (R) 162

163 T5D02 What formula is used to calculate voltage in a circuit? A. Voltage (E) equals current (I) multiplied by resistance (R) 163

164 T5D03 What formula is used to calculate resistance in a circuit? A. Resistance (R) equals voltage (E) multiplied by current (I) B. Resistance (R) equals voltage (E) divided by current (I) C. Resistance (R) equals voltage (E) added to current (I) D. Resistance (R) equals voltage (E) minus current (I) 164

165 T5D03 What formula is used to calculate resistance in a circuit? B. Resistance (R) equals voltage (E) divided by current (I) 165

166 T5D04 What is the resistance of a circuit in which a current of 3 amperes flows through a resistor connected to 90 volts? A. 3 ohms B. 30 ohms C. 93 ohms D. 270 ohms 166

167 T5D04 What is the resistance of a circuit in which a current of 3 amperes flows through a resistor connected to 90 volts? B. 30 ohms (R = E / I: 90 / 3 = 30 Ohms) 167

168 T5D05 What is the resistance in a circuit for which the applied voltage is 12 volts and the current flow is 1.5 amperes? A. 18 ohms B ohms C. 8 ohms D ohms 168

169 T5D05 What is the resistance in a circuit for which the applied voltage is 12 volts and the current flow is 1.5 amperes? C. 8 ohms (R = E / I: 12 / 1.5 = 8 Ohms) 169

170 T5D06 What is the resistance of a circuit that draws 4 amperes from a 12-volt source? A. 3 ohms B. 16 ohms C. 48 ohms D. 8 Ohms 170

171 T5D06 What is the resistance of a circuit that draws 4 amperes from a 12-volt source? A. 3 ohms (R = E / I: 12 / 1.5 = 8 Ohms) 171

172 T5D07 What is the current flow in a circuit with an applied voltage of 120 volts and a resistance of 80 ohms? A amperes B. 200 amperes C amperes D. 1.5 amperes 172

173 T5D07 What is the current flow in a circuit with an applied voltage of 120 volts and a resistance of 80 ohms? D. 1.5 amperes (I = E / R: 120 / 80 = 1.5 Amps) 173

174 T5D08 What is the current flowing through a 100- ohm resistor connected across 200 volts? A. 20,000 amperes B. 0.5 amperes C. 2 amperes D. 100 amperes 174

175 T5D08 What is the current flowing through a 100- ohm resistor connected across 200 volts? B. 2 amperes (I = E / R: 200 / 100 = 2 Amps) 175

176 T5D09 What is the current flowing through a 24- ohm resistor connected across 240 volts? A. 24,000 amperes B. 0.1 amperes C. 10 amperes D. 216 amperes 176

177 T5D09 What is the current flowing through a 24- ohm resistor connected across 240 volts? C. 10 amperes (I = E / R: 240 / 24 = 10 Amps) 177

178 T5D10 What is the voltage across a 2-ohm resistor if a current of 0.5 amperes flows through it? A. 1 volt B volts C. 2.5 volts D. 1.5 volts 178

179 T5D10 What is the voltage across a 2-ohm resistor if a current of 0.5 amperes flows through it? A. 1 volt (E = I X R: 0.5 X 2 = 1 Volt) 179

180 T5D11 What is the voltage across a 10-ohm resistor if a current of 1 ampere flows through it? A. 1 volt B. 10 volts C. 11 volts D. 9 volts 180

181 T5D11 What is the voltage across a 10-ohm resistor if a current of 1 ampere flows through it? B. 10 volts (E = I X R: 1 X 10 = 10 Volts) 181

182 T5D12 What is the voltage across a 10-ohm resistor if a current of 2 amperes flows through it? A. 8 volts B. 0.2 volts C. 12 volts D. 20 volts 182

183 T5D12 What is the voltage across a 10-ohm resistor if a current of 2 amperes flows through it? D. 20 volts (E = I X R: 2 X 10 = 20 Volts) 183